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Mapping UV properties throughout the Cosmic Horseshoe: lessons from VLT-MUSE

Mapping UV properties throughout the Cosmic Horseshoe: lessons from VLT-MUSE We present the first spatially resolved rest-frame ultraviolet (UV) study of the gravitationally lensed galaxy, the ‘Cosmic Horseshoe’ (J1148+1930) at z = 2.38. Our gravitational lens model shows that the system is made up of four star-forming regions, each ∼4–8 kpc2 in size, from which we extract four spatially exclusive regional spectra. We study the interstellar and wind absorption lines, along with C iii] doublet emission lines, in each region to investigate any variation in emission/absorption line properties. The mapped C iii] emission shows distinct kinematical structure, with velocity offsets of ∼±50 km s−1 between regions suggestive of a merging system, and a variation in equivalent width that indicates a change in ionization parameter and/or metallicity between the regions. Absorption line velocities reveal a range of outflow strengths, with gas outflowing in the range −200 ≲ v (km s−1) ≲ −50 relative to the systemic velocity of that region. Interestingly, the strongest gas outflow appears to emanate from the most diffuse star-forming region. The star formation rates remain relatively constant (∼8–16 M⊙ yr−1), mostly due to large uncertainties in reddening estimates. As such, the outflows appear to be ‘global’ rather than ‘locally’ sourced. We measure electron densities with a range of log (Ne) = 3.92–4.36 cm−3, and point out that such high densities may be common when measured using the C iii] doublet due to its large critical density. Overall, our observations demonstrate that while it is possible to trace variations in large-scale gas kinematics, detecting inhomogeneities in physical gas properties and their effects on the outflowing gas may be more difficult. This study provides important lessons for the spatially resolved rest-frame UV studies expected with future observatories, such as James Webb Space Telescope. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Monthly Notices of the Royal Astronomical Society Oxford University Press

Mapping UV properties throughout the Cosmic Horseshoe: lessons from VLT-MUSE

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References (46)

Publisher
Oxford University Press
Copyright
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
ISSN
0035-8711
eISSN
1365-2966
DOI
10.1093/mnras/sty315
Publisher site
See Article on Publisher Site

Abstract

We present the first spatially resolved rest-frame ultraviolet (UV) study of the gravitationally lensed galaxy, the ‘Cosmic Horseshoe’ (J1148+1930) at z = 2.38. Our gravitational lens model shows that the system is made up of four star-forming regions, each ∼4–8 kpc2 in size, from which we extract four spatially exclusive regional spectra. We study the interstellar and wind absorption lines, along with C iii] doublet emission lines, in each region to investigate any variation in emission/absorption line properties. The mapped C iii] emission shows distinct kinematical structure, with velocity offsets of ∼±50 km s−1 between regions suggestive of a merging system, and a variation in equivalent width that indicates a change in ionization parameter and/or metallicity between the regions. Absorption line velocities reveal a range of outflow strengths, with gas outflowing in the range −200 ≲ v (km s−1) ≲ −50 relative to the systemic velocity of that region. Interestingly, the strongest gas outflow appears to emanate from the most diffuse star-forming region. The star formation rates remain relatively constant (∼8–16 M⊙ yr−1), mostly due to large uncertainties in reddening estimates. As such, the outflows appear to be ‘global’ rather than ‘locally’ sourced. We measure electron densities with a range of log (Ne) = 3.92–4.36 cm−3, and point out that such high densities may be common when measured using the C iii] doublet due to its large critical density. Overall, our observations demonstrate that while it is possible to trace variations in large-scale gas kinematics, detecting inhomogeneities in physical gas properties and their effects on the outflowing gas may be more difficult. This study provides important lessons for the spatially resolved rest-frame UV studies expected with future observatories, such as James Webb Space Telescope.

Journal

Monthly Notices of the Royal Astronomical Society – Oxford University Press

Published: Feb 6, 2018

Keywords: gravitational lensing: strong; galaxies: evolution; galaxies: ISM; galaxies: star formation; ultraviolet: galaxies

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